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Generate RLE blocks in the encoder

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This commit is contained in:
bimbashrestha 2019-08-22 11:27:20 -07:00
parent c9072ee674
commit 4c90d862e3
1 changed files with 24 additions and 3 deletions
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27
lib/compress/zstd_compress.c
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@ -2323,6 +2323,15 @@ static void ZSTD_overflowCorrectIfNeeded(ZSTD_matchState_t* ms, ZSTD_CCtx_params
} }
} }
/* Returns true if the given block is a RLE block */
static int ZSTD_isRLE(const BYTE *ip, size_t length) {
if (length < 2) return 1;
size_t i;
for (i = 1; i < length; ++i) {
if (ip[0] != ip[i]) return 0;
}
return 1;
}
/*! ZSTD_compress_frameChunk() : /*! ZSTD_compress_frameChunk() :
* Compress a chunk of data into one or multiple blocks. * Compress a chunk of data into one or multiple blocks.
@ -2372,9 +2381,21 @@ static size_t ZSTD_compress_frameChunk (ZSTD_CCtx* cctx,
cSize = ZSTD_noCompressBlock(op, dstCapacity, ip, blockSize, lastBlock); cSize = ZSTD_noCompressBlock(op, dstCapacity, ip, blockSize, lastBlock);
FORWARD_IF_ERROR(cSize); FORWARD_IF_ERROR(cSize);
} else { } else {
U32 const cBlockHeader24 = lastBlock + (((U32)bt_compressed)<<1) + (U32)(cSize << 3); U32 cBlockHeader;
MEM_writeLE24(op, cBlockHeader24); /*
cSize += ZSTD_blockHeaderSize; We check to see if the regularly compressed block size is
less than 10 (the upper bound for RLE blocks) and we check
to see if the block is an RLE
*/
if (cSize < 10 && ZSTD_isRLE(ip, blockSize)) {
op[ZSTD_blockHeaderSize] = ip[0];
cBlockHeader = lastBlock + (((U32)bt_rle)<<1) + (U32)(blockSize << 3);
cSize = ZSTD_blockHeaderSize + 1;
} else {
cBlockHeader = lastBlock + (((U32)bt_compressed)<<1) + (U32)(cSize << 3);
cSize += ZSTD_blockHeaderSize;
}
MEM_writeLE24(op, (const U32) cBlockHeader);
} }
ip += blockSize; ip += blockSize;